The Learning Center
The actual U-value of a piece of insulating glass used in a typical window is dependent upon a number of variables, such as the number
of glass layers, coatings on the glass, and what type of gas is in the airspace. Generally, the values that are quoted for glass alone are
center-of-glass measurements and are not necessarily indicative of the entire piece of glass or the window performance as a whole.
This center-of-glass value drops off as you move towards the edge of the glass. The amount of drop off is dependent upon a number of
variables. It is not a good idea to compare the performance of one product to another based upon glass values alone. Most
manufacturers have run NFRC (National Fenestration Rating Council) thermal performance tests on an assembled unit, which is a
much better indicator of the unit’s overall performance compared to glass or window frame values alone.
8. What is the U-value of insulating glass?
< back to list of questions about glass
WINDOW GLASS
3245 Miracle Drive
Murrysville, PA 15668
724-387-2991
PA Contractor ID
PA001856